884 APPENDIX. 



also contains this body. Bile in the normal condition is free from sugar, so also is 

 urine, though this point has given rise to great dispute. 1 The disease diabetes is 

 characterized by an excess of dextrose in the fluids and tissues of the body (see p. 

 448). 



When pure, dextrose is colorless and crystallizes from its aqueous solution in 

 six-sided tables or prisms, often agglomerated into warty lumps. The crystals will 

 dissolve in their own weight of cold water, requiring, however, some time for the 

 process; they are very readily soluble in hot water. Dextrose is somewhat spar- 

 ingly soluble in alcohol, and crystallizes from anhydrous alcohol in prisms free from 

 water of crystallization ; it is, moreover, insoluble in ether. 



The freshly prepared cold aqueous solution of the crystals possesses a dextro-rotatory power of 

 +104 for yellow light. This, quickly on heating, more slowly on standing, falls to +56, at 

 which point it remains constant. 



Dextrose readily forms compounds with acids and many salts ; the latter are very unstable, 

 decomposition rapidly ensuing on heating them. When its metallic compounds are decom- 

 posed, the decomposition is, in many cases, accompanied by the precipitation of the metals, e. g., 

 silver, gold, mercury, bismuth. Caustic alkalies readily decompose them, as also does ammonia. 



Dextrose is readily and completely precipitated by lead acetate and ammonia. 



An important property of this body is its power of undergoing fermentations. 

 Of these the two principal are: 1. Alcoholic. This is produced in aqueous solu- 

 tions of dextrose, under the influence of yeast. The decomposition is the follow- 

 ing : C 6 H 12 6 = 2C 2 H 6 -f 2C0 2 , yielding (ethyl) alcohol and carbonic anhydride. 

 Other alcohols of the acetic series are found in traces, as also are glycerin, succinic 

 acid, and probably many other bodies. The fermentation is most active at about 

 25 C. Below 5 C. or above 45 C. it almost entirely ceases. If the saccharine 

 solution contains more than 15 per cent, sugar it will not all be decomposed, as 

 excess of alcohol stops the reaction. 2. Lactic. This occurs in the presence of 

 decomposing nitrogenous matter, especially of casein, and is probably the result 

 of the action of a specific ferment. 2 The first stage is the production of lactic acid, 

 C 6 H 12 6 2C 3 H 6 3 . In the second butyric acid is formed with evolution of hydro- 

 gen and carbonic anhydride : 2C 3 H 6 3 = C 4 H 8 2 +2C0 2 -|-4H. The above changes, 

 the first of which is probably undergone by sugar to a considerable extent in the 

 intestine, are most active at 35 C. ; the presence of alkaline carbonates is also 

 favorable. It is, moreover, essential that the lactic acid should be neutralized as 

 fast as it is formed, otherwise the presence of the free acid stops the process. 



The preparation, detection, and estimation of dextrose are so fully given in 

 various books that they need not be detailed here. 



2. Maltose. C 12 H 22 U +H 2 0. 



This form of sugar was first described by Dubrunfaut 3 as a product of the action 

 of malt extract on starch. Its existence was for a long time doubted until 0' Sul- 

 livan 4 repeated and confirmed the previous experiments. According to him it 

 crystallizes in fine acicular crystals, possesses a specific rotatory power of +150 and 

 a reducing power which is only one-third as great as that of dextrose. It seems 

 probable that this is the chief sugar obtained by the action not only of diastase 

 but of ptyalin and pancreatic ferment upon starch and perhaps also upon glycogen ; 5 

 although some dextrose may at the same time be formed. Musculus and Gruber 6 

 have shown that maltose may also be formed by the action of dilute sulphuric acid 

 on starch, and that it is capable of undergoing alcoholic fermentation. 



Preparation. See Musculus and Gruber (loc. cit.}. 



3. Milk-sugar. C 12 H 22 O n +H 2 0. 



Also known as lactose. It is found in milk, and is characteristic of this secre- 

 tion. It is said, however, to occur abnormally in the urine of lying-in women. 7 



It yields, when pure, hard, colorless crystals, belonging to the rhombic system 

 (four-sided prisms). It is less soluble in water than dextrose, requiring for solu- 



1 See Seegen, Der Diabetes Mellitus, 2 ed., S. 196. 



2 Lister, Path. Soc. Trans., vol. for 1878, p, 425, also Quart. Journ. of Micros. Sci., vol xviii. 

 (1878), p. 177. 



3 Ann. Chim. Phys. (3) xxi. (1847), p. 178. 



4 Journ. Chem. Soc , Ser. 2, vol. x. (1872), p. 579. 



5 Musculus u. v. Mering, Zeitschr. f. physiol. Chem., Bd. ii. (1878), S. 403. 



Zeitschr. f. physiol. Chem., Bd. ii. (1878), S. 177. 1 Hofmeister, Ibid., Bd. i. (1877), S. 101. 



